Rotary internal combustion engine

ABSTRACT

A rotary internal combustion engine comprising a casing providing a working space composed of intersecting cylindrical chambers, a power rotor disposed chamber, and a rotary abutment member disposed in the other chamber and intermeshing with the power rotor. The abutment member has five axial grooves inside its pitch circle. The grooves are at the bottoms thereof formed with part spherical cavities spaced from the axial ends of the member. The rotor has two or three lobes projecting outside its pitch circle and matching the grooves of the abutment. member. The tip chord of each lobe has a length corresponding to 35 percent to 40 percent of the distance between the centers of the cylindrical chambers. The axial length of the working space is about 90 percent of the opening chord of each groove. The angle between the cylindrical chambers in the point of intersection is about 74*.

United States Patent 1 7 Lundstriim et a1.

[ 1 Dec. 11, 1973 1 1 ROTARY INTERNAL COMBUSTION ENGINE [73] Assignee: Svenska Rotor Maskiner Aktiebolag,

Nacka, Sweden 1 2] Filed: Mar. 14,1972

1211 Appl. No.: 234,544

[30] Foreign Application Priority Data 3,401,676 9/1968 Wanzenberg 123/807 3,664,778 5/1972 Nilsson 418/117 3,491,730 1/1970 Nilsson 123/8.47

I Primary ExaminerC. J. Husar Attorney-Flynn & Frishauf [57] ABSTRACT A rotary internal combustionjengine comprising a casing providing a working space composed of intersecting cylindrical chambers, a power rotor disposed chamber, and a rotary abutment member disposed in the other chamber and intermeshing with the power rotor. "The abutment member has five axial grooves inside its pitch circle. The grooves are at the bottoms thereof formed with part spherical cavities spaced from the axial ends of the member. The rotor has two or three lobes projecting outside its pitch circle and matching the grooves of the abutment. member. The tip chord of each lobe has a length corresponding to 35 percent to 40 percent of the distance between the centers of the cylindrical chambers. The axial length of the working space is about 90 percent of the opening chord of each groove. The angle between the cylindrical chambers in the point of intersection is about 74.

16 Claims, 7 Drawing Figures PAIENIEDUEC 1 1 ms 3777 723 sum 2 or s PATENTEUHEB 1 1 ma SHEET 3 OF 5 3717723 SHEET l 0F 5 PATENTED DEL 1 1 I975 ROTARY INTERNAL COMBUSTKON ENGKNE Cross reference to related U.S. Pat. No. 3,491,730; and application Ser. No. 875,863 now US. Pat. No. 3,664,778. 7

The present invention relates to a rotary internal combustion engine of the type in which a power rotor has projecting lobes which mesh with matching grooves in a rotary abutment member.

Rotary internal combustion (lC) engines have been proposed which have a casing providing a working space, generally formed as two intermeshing cylindrical spaces, or chambers, which may be'two intersecting bores with parallel'axes cut into a casing block. A power rotor is disposed in one of the cylindrical chambers and has a plurality of axially extending lobes or lands, and intervening grooves or interspaces. A rotary abutment member is disposed in the other one of the chambers and has a plurality of axially extending lands, or lobes, separating intervening grooves or interspaces. The grooves or interspaces in the abutment member are shaped to mesh with the lobes or lands of the power rotor, and vice versa.

The power rotor and the ab'utment'member are so located in the chambers that the lobes of the power rotor are located outside the pitch circle of the power rotor. The lobe has two generally convex flanks separated by a generally part cylindrical tip portion coaxial with the p'owerrotor. Each flank of a lobe follows in profile a curve of generally part cylindrical tip portion coaxial with the power rotor. Each flank of a lobe follows in profile a'curve of generally epitrochoidal type generated by the edge portion of the mating flank ofa groove of the abutment member. Each depression of the abutment member is disposed inside the pitch circle thereof and has two generally concave flanks separated by a generally part cylindrical bottom portion coaxial with the member. The sides of the flank and the bottom portion of the abutment rotor do not come in sealing contact with the meshing lobe of the power rotor as the lobe of the power rotor m'oves'into and out of the groove of the abutment member. The engine also has means for charging and discharging gaseous combustion fluid into and out of the interspaces of the rotor and the grooves of the abutment member.

One basic problem in engines of this type is to reduce the leakage between the rotor and the abutment member themselves, and between those rotary members and the casing. Thus, the length of the sealing line should be as short as possible in relation to the displacement volume of each pair of a power rotor interspace or groove and an abutment rotor groove when they are in a position to form a closed operating chamber. The area of the grooves, in a transverse plane, is generally a second power function of the radial extent of the grooves; the length of the sealing line, however, is generally a first power function of said extent. Consequently, the radial extent of the grooves should be kept as large as possible, which means that the outer diameters of the power rotor and of the abutment member should be as large as possible in relation to the distance between their centers. This relation is depending upon the angle of intersection between the cylindrical intersecting chambers of the working space according to the well known cosine theorem. Furthermore, the area of each pair of communicating grooves is a fraction of the total area of the grooves forming closed operation chambers during one revolution of the power rotor.

This fraction is inversely proportional to the number of lobes of the power rotor. Thus, the number of lobes of the power rotor must be kept as low as possible. The displacement volume of the grooves is further directly proportional to the axial length of the power rotor. The sealing line is composed of two portions at the axial end planes of the closed chamber and of two portions extending axially between those planes. The change in length of the sealing line portions between the axial and planes is directly proportional to change in axial rotor length, whereas the length of the sealing line portions at the end planes is independent of the axial rotor length. The axial length of the rotor should thus be as large as possible. It has been found, however, that owing to combustion conditions, the axial length of the rotor should have a definite relation to the opening chord (that is, distance between edges of the flanks defining a groove) of the abutment rotor. This chord should consequently be as large as possible, which means that the number of grooves of the abutment member should also be as low as possible.

Another basic problem in such an engine is to provide as concentrated a combustion chamber as possible. This results in fast and complete combustion and low thermal losses, since the surface-to-volume ratio at maximum temperature is kept at a minimum. For this reason, the theoretical ratio between inlet volume and minimum volume of a closed operation chamber should be kept as high as possible. In fact, investigations have shown that a theoretical ratio of can be obtained. For this reason, the power rotor lobe should fill in the groove of the abutment member as much as possible when in position of full intermesh while, at the same time, the volume of a rotor interspace and an abutment member groove should be kept as high as possible. In the first instance, the length of the power rotor is thus of secondary importance in connection with this problem; however, in order to shield the stationary end walls of the casing from exposure to the hottest combustion gases as much as possible. the theoretical flank profile should be followed very closely at the axial ends of the abutment member. In order to achieve a high turbulence within the combustion chamber, the-gas must have a certain axial speed at least in angular positions shortly ahead of maximum intermesh. This can be obtained by providing a chamber-like additional space in form of a cavity in the bottom of the abutment member groove, located in axially central portion thereof.

The axial ends of the groove are not formed with this additional cavity but remain unrelieved, except for free running clearances, with regard to the theoretical shape developed by the meshing power rotor lobe. An especially good construction of the combustion chamber will be obtained if the tip of the rotor lobe is so wide that it restricts the combustion chamber in radial direction over as large an angular extent thereof as possible. For practical use, it has been found that the theoretical volume ratio defined above should at least be in the order of 20:1, preferably 40:1 or higher. This closely limits the combination and shape of the power rotor lobes and the abutment member grooves. Additionally, the power rotor and the abutment member must be designed in such a way that, for a certain real volume ratio between the inlet volume and the minimum volume, the size of the combustion chamber cavity is kept down to such a value that enough material is left to form a hub of the abutment member and to provide separating walls between adjacent cavities of sufficient dimension not only from a strength point of view but also to provide enough material to permit the formation of channels for cooling liquid and the like.

his an object of the present invention to provide a rotary internal combustion engine which incorporates optimum solutions to the conflicting requirements discussed above, in order to achieve a practicable, workable engine which is competitive to the well established reciprocating piston engines both with respect to economy as well as 'with respect to environmental pollution.

SUBJECT MATTER OF THE PRESENT INVENTION The center to center distance between the cylindrical chambers of the working space and the radii of the power rotor and the abutment member, respectively, are so interrelated that the angle between the respective tangents to the barrel walls of the cylindrical intersecting chambers in the point of intersection therebetween is of the order 65 to 80. With equal radii of the power rotor and the abutment member. This means for an angle of 65 that each of the radii is about 59 percent of the center distance and the radial extent of a power rotor lobe is about 16 percent of the outer diameter of the rotor, and for an angle of 80 that each of the radii is about 65 percent of the center distance and the radial extent ofa power rotor lobe is about 23 percent of the outer diameter of the roter. The radii mentioned must, however, not necessarily be equal but can vary such that one radius is only about 85 percent of the other radius. The number of the lobes of the power rotor and the number of grooves of the abutment member are arranged with respect to each other that the total number is less than ten, the number of grooves of the abutment member is greater than the number of lobes of the power rotor, and the difference being limited to a maximum of three. In accordance with a feature of the invention, a solution to the conflicting requirement results in a 3 arrangement, that is, three lobes of the power rotor and five grooves in the abutmentmember;2+3,2+4,2+5,and 3+4, 3+6, as well as 4 5 arrangements also yield commercially well acceptable results, although the 3 +5 arrangement appears preferable. Considerations of air flow, introduction of fresh air, scavenging of exhaust and the like leads to further considerations of relative sized and arrangements of the rotary members. Thus, the axial length of the working space is larger than 75 percent of the length of the opening chord of the groove of the abutment member; each groove of the abutment member has, at the bottom thereof, a cavity which is unrestrictedly open to the groove. The cavity extends axially only over a fraction of the total axial length of the abutment member, and radially towards the axis of the abutment member over a fraction of the distance from the bottom of the groove, at a location where the cavity is absent, to the axis of the abutment member, to leave sufficient material for a hub. V

The lobes of the power rotor are formed with generally part cylindrical tip portion coaxial with the rotor and separating the flanks of the lobe; the sum of the length of the tip chords of the power rotor lobes is preferably at least 50 percent of the distance between the centers of the bores forming the chambers. In an engine having a 3 5 configuration, the sum of the chord length is at least of the same order as the center distance between the rotary members; the axial length of the working space is less than the sum of the chord length.

The axial length of the working space and the rotary members is preferably between and 200 percent of the opening chord of a groove of the abutment member, preferably in the range of about -150 percent thereof. The cavity itself is preferably formed to be part spherical, to provide an essentially half spherical combustion chamber. Spark plugs are located on either, or both of the rotary members, the spark plugs being seated in a slight depression formed at the tip portion of the lobe of the power rotor, or on a slight projection formed in the cavity at the bottom of the groove of the abutment member. The power rotor carrying spark plugs, in cross section, will then have a tip portion which is somewhat undulating.

Sealing strips are provided at the edges of the flanks between which the grooves are formed in the abutment member. These sealing strips are biassed to come in contact with the mating flank of the lobe of the power rotor, during relative rotation.

In accordancewith a feature of the invention, two similar rotary engines are assembled coaxially with respect to each other, the rotors of one engine being offset with respect to the angular position of the rotor of another, to provide for smooth output torque. The casing then will have four chambers therein, a central separating wall, which is common to both engines, separating the engine assemblies from each other. More than two such engines can be stacked axially above each other, with various relative offsets of the angular positions of the lobes of the power rotors (and hence the grooves of the abutment members) to further improve the smoothness of the output.

The interrelationship of the dimensions of the relative elements and the lobes and interspaces of the power rotor, as well as the grooves and lands of the rotary abutment member, and the relationship to the axial position, and dimensions of the casing, as well these relationships with respect to the openings provided for inlet and outlet of fresh air, exhaust gases, and scavenging air will appear in greater detail as the specific description proceeds, when considered in connection with the accompanying drawings. The reason for the specific relationships, in the light of compromises which have to be made to obtain suitable compression, yet sufficient power output, and still have suffieicnt time for scavenging of exhaust gases and introducing fresh air, will also become apparent. In accordance with the invention, the various parameters are so selected that additional problems arising due to lack of perfect sealing, expansion of components due to operating temperatures, and particularly uneven, or differential expansion, are minimized.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 shows a transverse section of an engine according to the invention taken along the line 1-1 in FIG. 2;

FIG. 2 shows a longitudinal section taken along the line 2-2 in FIG. 1;

FIG. 3 shows a detail of FIG. 1 on a larger scale;

FIG. 4 shows a transverse section of a multiple engine according to the invention taken along the line 4-4 of FIG. 5;

FIG. 5 shows a longitudinal section taken along the line 5-5 in FIG. 4.

FIG. 6 shows a fractional transverse section of another engine according to the invention.

FIG. 7 shows a perspective view of an abutment member forming a part of the engine shown in FIGS. 1 to 3.

The engine shown in FIGS. 1 and 2 has a casing enclosing a working space 22 composed of two intersecting bores 24, 26 having parallel axes and intersecting along two straight axial lines 28, 30. The bores 24, 26 have a center to center distance D. and radii R and R respectively, with equal length of 0.625 D so that the angle a between the barrel walls of the lines 28, 30 of intersection is about 74. The axial length L of the working space 22 is 0.5 D The working space 22'has end walls 32, 34 (FIG. 2) and barrel walls 36, 38 (FIG. 1) surrounding the bores 24, 26. The casing 20 is provided with inlet channels 40, 42, 44, 46 (FIG. 2), with scavenging outlet channels 48, 50 and with exhaust ports49, 51 in the barrel walls 32, 34 andfurther with a fuel injection nozzle 52. A power rotor 54 is mounted in the casing 20 for sealing cooperation with the walls 32, 36 of the bore 24. A rotary abutment member, or

abutment rotor 56 is mounted in the casing 20 for sealing cooperation with the walls 34, 38 of the bore 26 and.

1 cave flanks 62, 64 (FIGS. l, 3) separated by a generally part-cylindrical bottom portion 66. Each abutment member land 58 is further provided with a partcylindrical tip portion 68 connecting the edges 70, 72 of the-flanks 62, 64 thereof. The opening angle [3 of each groove 60, i.e., the angle between rotor radii from the edge portions 70, 72 of the groove flanks 62, 64, is about 52, so that the length of the opening chord C is about 0.87 R, or 0.54 D,. A part-spherical cavity '74 is provided centrally in the'bottom portion 66 of each groove 60 which cavity-is unrestrictedly open and extending up into the adjacent flanks 62, 64 towards the groove 60 and has a maximum axial extent of about 80 percent of the length of the abutment member 56 and a maximum radial extent from the unrelieved bottom portion 66 of about 50 percent of the radial distance from the bottom portion 66 to the axis of the abutment member 56. In order to better illustrate the shape of the abutment member a perspective view thereof is shown in FIG. 7.

The power rotor 54 is provided with three lobes, or lands 76 and intervening grooves or interspaces 78 disposed outside the pitch circle of the power rotor 54, which circle practically coincides with the bottom circle of the rotor. Each lobe 76 is provided with two convex flanks 80, 82 separated by a generally partcylindrical tip portion 84. The tip portion 84 extends over an angle 7 of about 38, so that the length of the tip chord C is about 0.65 R or 0.40 D.. Each rotor interspace 78 is further provided with a part-cylindrical bottom portion 86 connecting the roots of the flanks 78, 80 thereof. Each flank 80, 82 of each rotor land 76 follows in a transverse plane a curve of generally epitrochoidal type generated by the cooperating edge portion 70, 72 of the abutment member flanks 62, 64, The

flanks 62, 64 and the bottom portion 66 of the abutment member 56, in a transverse plane, follow with a free running clearance therebetween, the envelope developed by the meshing lobe 76 of the power rotor 54 as the lobe 76 moves into and out of the groove of the abutment member as the power rotor 54 and the abutment member 56 rotate. The power rotor 54 is further provided with a power shaft 88 extending outside the casing 20. Furthermore, the power rotor 54 and the abutment member 56 are interconnected by a pair of intermeshing synchronizing gears 90, 92.

Operation of the engine:

A power rotor interspace 78 and an abutment member groove 60 are filled with fresh air through'the inlet channels 40, 42 and 44, 46, respectively. As the power rotor 54 and the abutment member 56 rotate, the interspace 78 and groove 60 are brought out of communication with the inlet channels 40, 42, 44, 46 and a charge of fresh air is trapped in the engine. During continued rotation, the abutment member land 58 preceding the charged abutment groove .60 projects into the power rotor interspace 78 and compression of the air starts. After a turning angle of the rotor 54 of about 33 the leading flank edge portion of the abutment groove 60 passes the intersection line 28 and the interspace 78 and groove 60 are brought into communication and form a common closed operation chamber. In a first phase, the closed operation chamber is defined by confronting surfaces of the power rotor 54, of the abutment member 56, the end walls 32, 34 and also by parts of the barrel walls 36, 38. During this first phase fuel is injected through the nozzle 52. The volume of the operation chamber decreases continuously. After a further turning of the rotor 54 of about 87 the trailing flank edge portion 72 of the abutment groove 60, that is, the flank of the next abutment land, passes the intersection line 28. A second phase starts. In this second phase of the closed'operation chamber, the margins thereof are defined by the confronting surfaces of the power rotor 54, of the abutment member 56 and of the end walls 32, 34 only. During this second phase the volume of the operation chamber further decreases continuously down to a minimum volume reached after further rotation of the power rotor 54 of about 18 when the lobe 76 of said power rotor 78 is in maximum intermesh with the rotary abutment groove 60. During this second phase of the operation chamber the ignition of the air-fuel mixture enclosed therein takes place preferably by means of one or more spark plugs 94, 96 carried by the abutment member 56 and/or the power rotor 54 (FIG. 3) and disposed in the cavity 74 of the abutment groove bottom portion 66 and/or the facing power rotor tip portion 84, respectively. In the position of maximum intermesh between the rotor lobe 76 and the abutment groove 60 more than 90 percent of the air-fuel mixture is enclosed within a space composed of the cavity 74. The portion of the groove 60 closed off by the part of the power rotor land tip portion 84 directly confronting the cavity 74 covers more than 90 percent of the opening area of the cavity 74. Thus a v very concentrated combustion chamber is provided. In

cavity 74 does not extend out to the axial ends of the abutment member 56. lncrease of the turbulence of the air-fuel mixture also results; the mixture, due to the compressing effect is axially accelerated centrally from each axial end, that is, towards the central portion of the abutment member 56. in combination with the intense turbulence in radial and peripheral directions upon entrance of the power rotor lobe 76 in the abutment groove 60, the total turbulence within the combustion chamber defined by the cavity 74 will thus be violent, resulting in rapid and complete combustion.

After the passage of the position of maximum intermesh the closed operation chamber increases in volume through athird phase. The position of the rotor and the abutment member corresponds to the mirror image of that in the second phase discussed above. Power rotor 54 has turned about 18 further up from dead center to the angular position, where the leading flank edge portion 70 of the abutment groove 60 passes the second intersection line 30. During this third phase the combustion is practically completed. The operation chamber then continues into a fourth phase corresponding to the first phase discussed above and during which the power rotor 54 turns over an angle of about 87 up to the angular position where the trailing flank edge portion 72 of the abutment groove 60 passes the second intersection line 30. During .this fourth phase the volume of the chamber increases continuously. After the trailing flank edge portion 72 has passed the second intersection line 30, the operation chamber is divided into two separate chambers, one comprising a complete groove 60 of the abutment rotor 56 and the ;other comprising most of interspace 78 of the power rotor 54. After a further rotation of the rotor 54 by about 33 the trailing flank edge portion 70 of the abutment member land tip portion 68, previously projecting into the rotor interspace 78 passes the second intersection line 30. The chamber defined by the interspace 78 of the power rotor 54 will have the complete volume of the interspace 78. After reaching this complete volume, the two chambers defined by the abutment member groove 60 and the power rotor interspace 78, respectively, are brought into communication with the corresponding exhaust ports 49, 51. Any remaining over-pressure in the chambers is relieved.

The interspace 78 and the groove 60 which had formed those chambers are then further brought into communication with the corresponding inlet channels 40, 42, 44, 46 and scavenging air outlet channels 48, 50. The channels have air forced therethrough to scavenge the depressions 78, 60 and to fill them with a new charge of fresh air. The cycle is then repeated.

The compression and expansion phases of the engine thus each comprise, with regard to the power rotor 54, an angular rotation thereof of about 138. The compression and expansion phases, with regard to the abutment member 56, comprise an angular rotation thereof of about 63, which corresponds to an angular rotation of the power rotor 54 of about 105. The gas exchange period: exhaust, scavenging and charging, of the engine comprises with regard to the power rotor 54 an angular rotation thereof of about 204, corresponding to an angle for the ports of the inlet and outlet channels 40, 42, 48 in the casing 20 of about 122. in practice, however, the expanded, still pressurized exhaust gases must be removed through the separate exhaust ports 49, 51 before communication between the interspace 78 and the groove 60 and the inlet and outlet channels 40, 42, 48 is established. Otherwise the exhaust gas will blow back into the inlet channels 40, 42 and considerably interfere with scavenging. The angle of the inlet and outlet channel ports can, for this reason, be reduced to about With regard to the abutment member 56, the gas exchange phase can extend about 234 of the rotation of the abutment 56; this corresponds to 390 of power rotor 54 rotation and to an angle for the ports of the inlet and outlet channels 44, 46, 50 in the casing 20 of about 182. Thus, sufficient time and space for effective scavenging of the abutment grooves 60 is available. The angular extent of the ports of the inlet and outlet channels 44, 46, 50 can be less than the available angle in order to reduce the power required by the scavenging pump without reduction of the scavenging effect.

The power rotor 54 and the rotary abutment 56 cooperating therewith, each having a certain radius R and R respectively, located on a fixed center distance D might be designed in different ways. An increase of the angular extent of the tip portion 84 of the rotor 54 means a corresponding reduction of the angular extent of the tip portion 68 of the abutment 56 and vice versa.

If the angular extent of the power rotor tip portion 84 is changed, the angle required for the ports of the inlet and outlet channels 40, 42, 48 changes at double the rate as that of the angle of the power rotor tip portion. Change of the angular extent of the power rotor tip portion 84 further influences the area of the abutment member groove 60 open towards the end walls 32, 34 in the position of maximum intermesh, with a minimum value for a rotor tip portion 84 extending over an angle of about 27.

As noted above, the power rotor tip portion 84 practically completely covers the opening of the abutment cavity 74. This is advantageous not only with regard to the geometrical configuration of the combustion chamber but also for the reason that the surface of the power rotor tip portion 84, in the same way as the surfaces of the cavity 74, is never in contact with any sealing element sliding along the surface, as are the rotor flanks 80, 82. The surfaces forming the margins of the combustion chamber can thus be provided with a heat insulating coating in order to reduce the heat losses from the gas during combustion. An increase of the peripheral extent of the power rotor tip portion 84 means a reduction of the displacement volume of the engine; thus the peripheral extent should not be too large. There are also other considerations regarding the peripheral extent of the power rotor tip portion 84 (such as capability of machining). The embodiment disclosed forms an optimum solution with regard to all those factors.

As the total displacement volume of the engine obtained during one revolution of the power rotor 54 varies relatively little with the number of the lands 76 on the power rotor 54, as long as the rotor and abutment radii and length and the center distance is kept constant, it is important to provide a power rotor 54 with as few lands 76 as possible so that the displacement volume of a rotor interspace 78 and the abutment groove 60 communicating therewith is kept as high as possible. The ratio between the length of the sealing lines of the operation chamber formed by the power rotor interspace and the abutment groove can thus be minimized, which is important with regard to the reduction of the sealing losses. in order to obtain a sufficient scavenging period it is, however, necessary to have at least two power rotor lands 76; perferably this number should be three.

The cross-sectional outline of the lobe 76 of the power rotor will, at the tip'portion, be somewhat undulating (FIG. 3) so that the spark plug can be placed in a somewhat depressed position with respect to the outermost limits of the power rotor. Conversely, spark plug 94 located in the groove of the abutment'memb'er will project into the cavity formed in the bottom of the groove of the abutment member. This projection of the spark plug into the abutment member further increases turbulence. The spark plug itself can be located in a small projection 94' (FIG. 3) formed within the cavity. The spark plugs have been omitted from the illustrations in FIGS. 1 and 2 for simplicity; likewise, ducts which may carry gaseous orliquid cooling fluid to the interior of the abutment members have been omitted.

The tests run on an actually built test unit having the lobe and groove combination 3 5, a center to center distance of 240 mm, equal radii of the power rotor and the abutment member of 150 mm and an axial length of the working space of 120 mm indicates that with a speed of the power rotor of 2,000 to 3,000 rpm the power produced will be of the order 200 to 300 H and the maximum efficiency of about 27 percent with very small directions therefrom at part loads.

An engine of the type shown in FIGS. 1- and 2 will fire three times for each'revolution of the power rotor 54 and the torque will thus vary with a 120 period. FIGS. 4 and show an engine which has more uniform torque and provides larger output power with a minimum increase of the bulk and weight. The engine has at least two power rotors 54, 54a of identical shapes, each cooperating with a meshing abutment member 56, 56a.

The rotors 54, 54a are coaxial and non-torsionally so interconnectedthat the different rotors 54, 54a are angularly displaced correspondingly to a fraction of the angular pitch, which fraction is "the inverse number of the rotors 54, 54a. A separating wall (FIG. 5) separates the combustion chambers and is common to both chambers.

The power rotor and the abutment member shown in FIG. 6 differ from the ones shown in FIGS. 1 and 3 in the following respect. The power rotor- 8 is provided with two lobes 100 and intervening grooves or interspaces 102. Each lobe 100 is provided with two generally convex flanks 104, 106 and a separating tip portion 108 cylindrical around the axis 110 of the rotor 5 8. The lobes are completely disposed outside the pitch circle 112 of the rotor 98 and separated by bottom portions 114 of the interspaces 102 cylindrical around the axis 110 of the rotor 98. The rotary abutment member 116 is provided with five grooves 120 and intervening lands 118. Each groove 120 is provided with two concave flanks 122, 124 and a separating bottom portion 132 cylindrical around the axis 128 of the abutment member 116. The grooves 120 are completely disposed inside the pitch circle 130 of the abutment member 116 and separated by tip portions 126 of the intervening land 118 cylindrical around the axis 128 of the abutment member 116. In the bottom 132 of each groove 120 of the abutment member 116 and extending partly up into the flanks 122, 124 thereof a generally part spherical cavity 134 is formed and extending in axial direction over a centralportion of the abutment member 116 only and in radial direction over a fractionof the distance from the unrelieved bottom portion to the axis 128 of the abutment member 116.

As the general shape of the power rotor 98 differs from that of the power rotor 54 shown in FIGS. 1 and 3 the specific turning angles given above'with regardto the power rotor 54 will be completely different'which also means that the porting of the casing of the engine will be different even-though the principal arrangement thereof can be the same.

Various changes and modifications can be -made within the inventive concept We claim:

1. Rotary internal combustion engineof the'type comprising a casing providing a working space, generally composed of two intersecting cylindrical chambers with parallel axes,

a power rotor disposed in one of said chambers having a plurality of axially extending lobes and interspaces,

and a rotary abutment member disposed in the other one of. said chambers having a plurality of axially extending grooves and intervening lands intermeshing with the lobes and interspaces of the rotor,

each lobe of the rotor being disposed outside the pitch circle of the rotor, each lobe having twogenerally convex flanks separated by a, generally partcylindrical tip portion coaxial with the rotor,each flank in profile following a curve of generally e'pitrochoidal type generated by the edge portion of themating flank of a groove of the abutment member,

said abutment member being provided with a plurality of grooves disposed inside the pitch circle of the abutment member, each groove having two generally concave flanks separated by a generally partcylindrical bottom portion coaxial with the abutment member, each flank and the bottom portion being disposed out of sealing adjacency to the meshing lobe of the rotor as said lobe of the rotor moves into and out of the. groove of the abutment member, respectively,

and further comprising means for charging and discharging each of said rotor interspaces and of said abutment member grooves,

wherein the angle of intersection between the cylindrical intersecting chambers is of the order 65 to 80,

the total number of lobes and grooves of the rotor and of the abutment member, respectively, is less than 10,

the number of grooves of the abutment member is greater than the number of lobes of the rotor with the difference between those numbers beinglimited to a maximum of three,

the axial length of the working space is larger than percent of the length of the opening chord of the groove of theabutment member,

and each groove of the abutment member at the bottom portion thereof is formed with a cavity unrestrictedly open to the groove and extending axially over a fraction of the total axial length of the abutment member and radially towards the-axis of the abutment member over a fraction of the distance from the bottom of the groove, at a location where the cavity is absent, to the axis of the abutment member.

2. Engine as defined in claim 1, in which the sum of the lengths of the tip chords of the power rotor lobes is at least 50 percent of the distance between the centers of the cylindrical chambers.

3. Engine as defined in claim 2, in which the number of the grooves of the abutment member is five.

4. Engine as defined in claim 3, in which the length of each of said tip chords of the power rotor lobes is between 33 and 55 percent of said center distance thereof.

5. Engine as defined in claim 4, in which the length of each of said tip chords of the power rotor lobes is between 37.5 and 52.5 percent of said center distance.

6. Engine as defined in claim 4, in which the axial length of the working space is between 75 and 200 percent of said opening chord of the abutment member groove.

7. Engine as defined in claim 6, in which the axial length of the working space is between 100 and 150 percent of said opening chord of the abutment member groove.

8. Engine as defined in claim 4, in which the power rotor has three lobes and the length of the working space is less than said sum of the lengths of the tip chord of the rotor lobes.

9. Engine as defined in claim 8, in which the outer diameter of the abutment member is substantially equal to the pitch diameter of the abutment member.

10. Engine as defined in claim 9, in which the outer diameter of the power rotor is about equal to that of the abutment member.

11. Engine as defined in claim 1, in which said cavity is part-spherical.

12. Engine as defined in claim 1, in which spark plugs are carried by at least one of the power rotor and the abutment member,

each spark plug being located in an axially central portion of the carrying member and projecting into the cavity in the groove of the abutment member.

13. Engine as defined in claim 12, in which each rotor lobe tip portion is formed with a depression, and a spark plug is located in said depression.

14. Engine as defined in claim 12, in which each cavity in the grooves of the abutment member is formed with a projection, and a spark plug is located at said projection.

15. Engine as defined in claim 1, comprising at least two power rotors of identical shape,

each cooperating with a meshing abutment member and coaxially, non-torsionally interconnected, respective coaxial rotors being angularly displaced correspondingly to a fraction of the angular pitch, said fraction being the inverse number of the rotors.

16. Engine according to claim 1, wherein the means discharging burnt exhaust gases comprises a port formed in the walls of each cylindrical chamber and open to the chamber, and in gas communication with an interspace of the power rotor and a groove of at least one of the abutment member, respectively, when the interspace or groove has reached a first rotary position in the casing at which the lobe of the power rotor is out of engagement with the groove of the abutment member;

a second port in the wall of the cylindrical chamber and open to the chamber and in gas communication with the cooperating interspace or groove when the interspace or groove has reached a second rotary position beyond said first rotary position;

a third port located in the wall of the cylindrical chamber and open to the chamber and in gas communication with the interspace or groove at said second position,

and means introducing scavenging gas, under pressure, into the interspace or groove through said second port, to be exhausted through said third port.

NITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,777 ,723 Dated December 11 1973 I Inventor(s) JAN -BORJE LUNDSTRCISM et al I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Left Column cover page replace the line following;

" [30] Foreign Application Priority Data" with -Mar.- 17 and Apr. 13 1971 Great Britain. .7 ,o79-/7.1--.

Column 4 line 49 replace "suffieicnt" with -sufficient-- 1 Column 9 line 28 replace "directions" with -deviations----.

Signed and sealed this 16th day of July 1974.

(SEAL) Attest:

c. MARSHALL'DANN MCCOY M. GIBSON, JR.

Commissioner of Patents Attesting Officer USCOMM-DC 6O376-P69 0.5. GOVIRNHENT PRINTING OFFICE: I969 0-366-334.

=ORM PD-IOSO (10-69) 

1. Rotary internal combustion engine of the type comprising a casing providing a working space, generally composed of two intersecting cylindrical chambers with parallel axes, a power rotor disposed in one of said chambers having a plurality of axially extending lobes and interspaces, and a rotary abutment member disposed in the other one of said chambers having a plurality of axially extending grooves and intervening lands intermeshing with the lobes and interspaces of the rotor, each lobe of the rotor being disposed outside the pitch circle of the rotor, each lobe having two generally convex flanks separated by a generally part-cylindrical tip portion coaxial with the rotor, each flank in profile following a curve of generally epitrochoidal type generated by the edge portion of the mating flank of a groove of the abutment member, said abutment member being provided with a plurality of grooves disposed inside the pitch circle of the abutment member, each groove having two generally concave flanks separated by a generally part-cylindrical bottom portion coaxial with the abutment member, each flank and the bottom portion being disposed out of sealing adjacency to the meshing lobe of the rotor as said lobe of the rotor moves into and out of the groove of the abutment member, respectively, and further comprising means for charging and discharging each of said rotor interspaces and of said abutment member grooves, wherein the angle of intersection between the cylindrical intersecting chambers is of the order 65* to 80*, the total number of lobes and grooves of the rotor and of the abutment member, respectively, is less than 10, the number of grooves of the abutment member is greater than the number of lobes of the rotor with the difference between those numbers being limited to a maximum of three, the axial length of the working space is larger than 75 percent of the length of the opening chord of the groove of the abutment member, and each groove of the abutment member at the bottom portion thereof is formed with a cavity unrestrictedly open to the groove and extending axially over a fraction of the total axial length of the abutment member and radially towards the axis of the abutment member over a fraction of the distance from the bottom of the groove, at a location where the cavity is absent, to the axis of the abutment member.
 2. Engine as defined in claim 1, in which the sum of the lengths of the tip chords of the power rotor lobes is at least 50 percent of the distance between the centers of the cylindrical chambers.
 3. Engine as defined in claim 2, in which the number of the grooves of the abutment member is five.
 4. Engine as defined in claim 3, in which the length of each of said tip chords of the power rotor lobes is between 33 and 55 percent of said center distance thereof.
 5. Engine as defined in claim 4, in which the length of each of said tip chords of the power rotor lobes is between 37.5 and 52.5 percent of said center distance.
 6. Engine as defined in claim 4, in which the axial length of the working space is between 75 and 200 percent of said opening chord of the abutment member groove.
 7. Engine as defined in claim 6, in which the axial length of the working space is between 100 and 150 percent of said opening chord of the abutment member groove.
 8. Engine as defined in claim 4, in which the power rotor has three lobes and the length of the working space is less than said sum of the lengths of the tip chord of the rotor lobes.
 9. Engine as defined in claim 8, in which the outer diameter of the abutment member is substantially equal to the pitch diameter of the abutment member.
 10. Engine as defined in claim 9, in which the outer diameter of the power rotor is about equal to that of the abutment member.
 11. Engine as defined in claim 1, in which said cavity is part-spherical.
 12. Engine as defined in claim 1, in which spark plugs are carried by at least one of the power rotor and the abutment member, each spark plug being located in an axially central portion of the carrying member and projecting into the cavity in the groove of the abutment member.
 13. Engine as defined in claim 12, in which each rotor lobe tip portion is formed with a depression, and a spark plug is located in said depression.
 14. Engine as defined in claim 12, in which each cavity in the grooves of the abutment member is formed with a projection, and a spark plug is located at said projection.
 15. Engine as defined in claim 1, comprising at least two power rotors of identical shape, each cooperating with a meshing abutment member and coaxially, non-torsionally interconnected, respective coaxial rotors being angularly displaced correspondingly to a fraction of the angular pitch, said fraction being the inverse number of the rotors.
 16. Engine according to claim 1, wherein the means discharging burnt exhaust gases comprises a port formed in the walls of each cylindrical chamber and open to the chamber, and in gas communication with an interspace of the power rotor and a groove of at least one of the abutment member, respectively, when the interspace or groove has reached a first rotary position in the casing at which the lobe of the power rotor is out of engagement with the groove of the abutment member; a second port in the wall of the cylindrical chamber and open to the chamber and in gas communication with the cooperating interspace or groove When the interspace or groove has reached a second rotary position beyond said first rotary position; a third port located in the wall of the cylindrical chamber and open to the chamber and in gas communication with the interspace or groove at said second position, and means introducing scavenging gas, under pressure, into the interspace or groove through said second port, to be exhausted through said third port. 